1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a reflective-type liquid crystal display device which is provided with reflective electrodes which can efficiently reflect incident light particularly from an observation side thus enhancing the visibility.
2. Description of the Related Art
In a liquid crystal display device, a liquid crystal layer is sandwiched between a pair of substrates made of glass or the like which have electrodes for forming pixels and switching elements and images which are electronically formed are visualized by irradiating an external light. A driving method of this type of liquid crystal display device is roughly classified into two methods. Spacers which are made of epoxy resin, glass or the like and are formed in a bead shape or in a columnar shape may be interposed between both substrates to ensure a gap between both substrates. When the spacers are formed in a bead shape, they are referred to as “spacer beads”.
One of these methods is a so-called simple-matrix-type in which a large number of linear electrodes which cross each other are formed on respective inner surfaces of a pair of substrates and pixels are formed on the crossing portions and the other method is an active-matrix-type in which a large number of switching elements such as thin film transistors for selecting respective pixels are arranged in a matrix array.
With respect to electronic equipment such as portable information terminals (so-called PDA (Personal Digital Assistant)) and portable telephones, which are required to consume small power, as a liquid crystal display device which constitutes an image monitor of such an electronic equipment, a reflective-type liquid crystal display device or a semi-transmissive/reflective-type liquid crystal display device has been widely adopted. The reflective-type liquid crystal display device includes a reflective film, a reflective electrode or a reflective plate on an inner surface or a back surface of a substrate opposite to an observation-side substrate (hereinafter, referred to as “one substrate”). Here, light (ambient light) which is incident from the observation-side substrate (hereinafter referred to as “another substrate”) is reflected on the above-mentioned reflection film or the like, is made to pass through a liquid crystal layer, and is subjected to the intensity modulation with electronic images formed in the liquid crystal layer, and is irradiated from the above-mentioned another substrate whereby the electronic images are visualized.
Further, there has been known a liquid crystal display device which adopts a display method called a semi-transmissive/reflective type display method which provides light transmission apertures or slits in portions of the reflective film or the like and light from a back surface of the above-mentioned one substrate is made to pass through the light transmission apertures toward the other substrate side and is visualized. Here, the reflective-type liquid crystal display device which will be explained hereinafter in conjunction with this specification and drawings is also applicable to the above-mentioned semi-transmissive/reflective type liquid crystal display device.
There has been proposed a liquid crystal display device which forms reflective electrodes having rough surfaces by forming a resin layer (resin binder layer) having a rough surface on one substrate and forming reflective films (hereinafter also referred to as “reflective electrodes” or “metal reflection films”) on the resin layer (Japanese Patent Laid-open No. 75237/1994, Japanese Patent Laid-open No. 218906/1995, Japanese Patent Laid-open No. 258617/1999, Japanese Patent Laid-open No. 316371/1999). Further, there has been also proposed a liquid crystal display device which forms the rough surface on reflective electrodes and enhances the reflection efficiency by scattering fine particles (hereinafter referred to as “beads”) made of resin material or the like and forming the reflective electrodes on the beads (Japanese Patent Laid-open No. 323196/1999, Japanese Patent Laid-open No. 330106/1999).